This application relates to an apparatus and method for measuring geomagnetically induced currents (GIC), and more particularly, to an apparatus and method for measuring DC currents that flow through high voltage transmission conductors when solar storms are active.
Solar Flares on the run result in an ejection of charge which, when it travels past the earth, results in a disruption of the earth's magnetic field. This disruption results in potential differences along the length of transmission lines, which, in turn, results in current flow. These currents vary slowly with time and, once they are induced into the transmission system, for all intents and purposes can be considered to be DC currents.
These DC currents often flow to earth through transmission transformer windings, resulting in saturation of the transformer cores which results in heating, harmonics, vibration, and Volt Ampere Reactive (VAR) consumption. This saturation can lead to system degradation and voltage collapse and/or transformer heating which can lead to premature aging or failure. As a result, a considerable effort is underway to fully understand the phenomena, its impact, and what mitigation procedures or technologies can be applied.
An important part of understanding the phenomena as well as implementing mitigation procedures is measuring the magnitudes of these DC currents. To date all measurements have been performed by measuring the DC currents in the neutral of transformers because (a) access is possible, (b) it is at low voltage, and (c) the data is easy to integrate into a measurement system. The challenge of this measurement approach is that no knowledge is obtained as to what the level of DC currents are in the individual phases.
Accordingly, there is a need for an apparatus and method that measures the DC current on a high voltage conductor for transformer configurations in which the induced DC current does not flow to earth ground.